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Acetylcholinesterase (AChE) plays a crucial role in regulating the levels of the neurotransmitters in organisms. In this study, a dual-optical signals ratiometric sensing system based on fluorescence and scattered light was constructed by using silicon quantum dots (SiQDs) and MnO2 nanosheets for AChE activity assay. The two independent signals of fluorescence and scattering can be collected at the same excitation wavelength, which not only improves the accuracy of detection but also greatly simplifies the experimental operation. In this study, the SiQDs with excellent optical properties were successfully prepared by one-step hydrothermal method and the optimal emission peak was located at 445 nm. The fluorescence signal of SiQDs could be suppressed via MnO2 nanosheets on account of the inner filter effect (IFE). In addition, MnO2 nanosheets could provide a size-regulated second-order scattering (SOS) signal at 725 nm. Therefore, MnO2 nanosheets could play the dual roles of fluorescence signal quencher and SOS signal donor. AChE could act on the substrate acetylthiocholine (ATCh) and make it to engender thiocholine (TCh), which will triggered the reduction of MnO2 nanosheets, resulting the decompostion of MnO2 nanosheets. At the same time, the fluorescence of SiQDs recovery and the SOS signal decline. Thus, the ratiometric sensing analysis of AChE activity was achieved according to the opposite responses of fluorescence and scattering dual signals. Under the optimal conditions, an excellent linearity for AChE from 0.5 to 80.0 U/L and high sensitivity with a detection limit of 0.16 U/L were achieved. The practical application of the established method was assessed and verified by analyzing of AChE activity in human serum, and obtained satisfactory results. The proposed dual-optical signals ratiometric analytical strategy exhibits the merits of simple operation, high sensitivity and excellent selectivity, indicating that it has great application potential in diagnosis the AChE-related diseases. Furthermore, an innovative logic gate device was designed based on dual-optical signals, which has great value for the development of artificial intelligence analysis equipment to monitor AChE activity.

In present study, DL-lactic acid/trioctylmethylammonium chloride-based deep eutectic solvent (DES), which was considered as an environmental friendly extraction solvent to replace traditional organic reagent, was firstly presented for monitoring of trace cadmium (Cd) and arsenic (As) in wine samples by ultrasonic-assisted dispersive liquid-liquid microextraction (UA-DLLME) method. Moreover, different extraction conditions, including the type and volume of DES and dispersive solvent, pH of the solution, salt amount, time of vortex and sonication, were systematically evaluated. At the optimized extraction conditions, good linear relationships (0.50–8.0 μg·L−1 for Cd, 2.0–50 μg·L−1 for As) were obtained and limits of detection of Cd and As were 0.080 and 0.30 μg·L−1, respectively. In addition, the accuracy (as recoveries %), and intra-/inter-day precision (as relative standard deviation %) were in the ranges of 90.6–103.6% and 2.9–4.5%, respectively. Finally, the proposed method was applied to analyze 6 kinds of wine samples, which possessed wide practical application value in monitoring heavy metal residues in wine and even complex food matrices.

An efficient dispersive liquid-liquid microextraction (DLLME) method based on the solidification of floating organic drop (SFO) has been developed for extraction of bisphenol S (BPS), bisphenol A (BPA) and bisphenol B (BPB) in canned fruit, in which green deep eutectic solvent (DES) was used as the extraction solvent. The analysis was determined by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). All parameters affecting the extraction efficiency, including selection of DES, volume of DES, salt effect, extraction time, pH, and dispersion solvent type and volume, were investigated and optimized. The extraction efficiency of bisphenols was improved by a menthol-based DES. More importantly, the low melting point of DES makes the extracted bisphenols could be easily separated from sample solution with a syringe. This method showed good linearity (r > 0.9916) in the range of 10.0–200 ng g−1 with limits of detection (LODs) ranged from 1.5 to 3.0 ng g−1 and the limit of quantifications (LOQs) were ranged from 5.0 to 10.0 ng g−1. The recoveries of three spiked levels were ranged from 79.5% to 101% with relative standard deviations (RSDs) were lower than 4.6%. This developed method was successfully applied in bisphenols extraction of different canned fruit samples and exhibited a simple and green extraction procedure. This environmentally friendly method offers an important reference for the separation of bisphenols in food.

The silica-coated magnetic graphene oxide (Fe3O4-GO@SiO2) composites were synthesized by a simple procedure in this work. The nanocomposite was characterized and applied for the rapid magnetic solid-phase extraction (MSPE) of chromium (Cr), cobalt (Co), nickel (Ni), copper (Cu), cadmium (Cd), lead (Pb), silver (Ag) ions at trace level in environmental water samples. Various experimental parameters affecting the extraction efficiency of the target metal ions by Fe3O4-GO@SiO2 were investigated and optimized, including sorbent dosage, pH of sample solution, sorption time, volume and eluent concentration, as well as elution time. Under the optimal conditions, the limits of detection (LODs, 3σ) for the target analytes were obtained in the range of 2.023–13.810 ng L−1. The recoveries of the target metals in four environmental water samples ranged from 83% to 109% and the relative standard deviations (RSDs) were lower than 7%. Moreover, in batch adsorption experiments, the adsorption of these seven metal ions was relatively speedy and the equilibrium was established after shaking 35 min which kinetics followed the pseudo second-order model, indicating a chemisorption nature. The adsorption process was simulated by the Langmuir isotherm accurately, and the calculated maximum adsorption (qmax) capacities of Fe3O4-GO@SiO2 were 182.98 mg g−1, 116.35 mg g−1, 226.08 mg g−1, 149.59 mg g−1, 100.81 mg g−1, 168.55 mg g−1 and 141.09 mg g−1 for Cr (III), Co (II), Ni (II), Cu (II), Cd (II), Pb (II) and Ag (I), respectively. Finally, the developed method was successfully applied for simultaneous and sensitive determination of target metals at trace level in environmental water samples.